Semester 1 Final: Metabolism

Question 1

Metabolic Pathways

Answer 1

a molecule is altered through a series of steps resulting in a specific product
-Catalyzed by enzymes

Question 2

Catabolic Pathways

Answer 2

release energy by breaking down molecules (exergonic)

Question 3

Anabolic Pathways

Answer 3

consume energy to build complicated molecules from simpler ones (endergonic)

Question 4

1st Law of Thermodynamics

Answer 4

Energy of the universe is constant so it can be transferred or transformed but not created or destroyed

Question 5

2nd Law of Thermodynamics

Answer 5

Every energy transformation leads to increased entropy

Question 6

Free Energy

Answer 6

The portion of energy within a system that is free to do work (symbolized by G)

Question 7

Exergonic Reactions

Answer 7

the process is spontaneous and releases energy
-decreases the system’s free energy (ΔG is negative) and increases entropy
– The final state of energy is less likely to change & is more stable
– reactants, or initial state, has more free energy than the products, or final state

Question 8

Endergonic reactions

Answer 8

– the process requires energy input & increases the system’s free energy, decreasing entropy (nonspontaneous)
– products, or final state, have more free energy than the reactants, or initial state

Question 9

Metabolism

Answer 9

• All the chemical reactions occurring in an organism

– Follow metabolic pathways

Question 10

ATP & Energy Coupling

Answer 10

Exergonic processes drive endergonic ones
– ATP is responsible for most coupling in cells and acts as the immediate power source for work
– hydrolysis of ATP provides the free phosphate that will be used to phosphorylate other molecules
-phosphorylated molecule is less stable & more reactive & this change allows it to perform work

Question 11

Enzymes

Answer 11

Catalytic proteins that speed up specific reactions without being consumed
-lower activation energy of chemical reactions

Question 12

Induced fit

Answer 12

active sites are not rigid but change shape slightly once chemical interactions occurs with the substrate to ensure a snug fit
(ie handshake)

Question 13

How do enzymes lower activation energy?

Answer 13

1. Acting as a template for substrate orientation
2. Stressing the substrate by bending critical bonds
3. Providing a favorable mini-environment, such as a pH pocket
4. Participating directly in the catalytic reaction by
   providing temporary covalent bonding; substrate is unstable and will form new bonds to be converted into product

Question 14

effect of temperature on enzyme functionality

Answer 14

– Reaction rates increase with higher temperatures because substrates collide with active sites more frequently (greater kinetic/heat energy)
– Only works to a point because too high of a temperature will cause enzyme denaturation

Question 15

effect of pH on enzyme functionality

Answer 15

There are optimal pH range because too acidic an environment will cause denaturation
– Example: Pepsin works at pH 2 because functions in
our stomach & trypsin works at pH 12 works in the alkaline environment of the small intestine

Question 16

effect of cofactors on enzyme functionality

Answer 16

Non protein that all function in various ways to increase enzymatic productivity
– Inorganic cofactors examples are Cu, Fe, Zn
– Organic cofactors (coenzymes) such as vitamins

Question 17

effect of inhibitors on enzyme functionality

Answer 17

Chemicals that selectively inhibit the actions of enzymes
– Are reversible if bond with a weak bond, but can be irreversible if covalently bonded
Many inhibitors are naturally occurring in the cell

Question 18

Competitive Inhibitors

Answer 18

Resemble the normal substrate & compete for admission into active site
ex. penicillin

Question 19

Noncompetitive Inhibitors

Answer 19

Molecules that bind to a portion of the enzyme away
from the active site (allosteric site)
– Cause the enzyme to change shape & the active site becomes unreceptive
– Ex. DDT

Question 20

Feedback Inhibition:

Answer 20

A metabolic pathway is switched off by its end product
• Product inhibits an enzyme in its own pathway by noncompetitive inhibition
– Prevents unnecessary waste from excess products